Timeout with Promise

Question

Timeout with Promise

I'm looking to enhance my understanding of working with promises by rewriting this function to resolve the promise instead of resorting to calling the callback function.

export const connect = (callback: CallableFunction|void): void => {
    LOG.debug("Connecting to DB at %s", URI);

    connectToMongoDb(URI, opts)
        .then((result) => {
            LOG.debug("Connection established");
            connection = result;

            if (callback) {
                callback();
            }
        })
        .catch((err) => {
            LOG.error("Could not establish connection to %s, retrying...", URI);
            LOG.error(err);
            setTimeout(() => connect(callback), 5000);
        });
};

Despite several attempts, I have been unable to do so. My initial approach was:

export const connect = (): Promise<void> => new Promise((resolve): void => {
    // ...´
        .then((result) => {
            LOG.debug("Connection established");
            connection = result;
            resolve();
        })
    // ...
});

Unfortunately, this method does not properly resolve when the connection is established.

What could be the issue here? How can I rephrase this to effectively utilize and resolve the Promise without the need for a callback function?

typescript promise callback settimeout

Answer 1

Answer №1

Upon reviewing the feedback, I successfully restructured the function to ensure it returns a promise that resolves only when the connection is established:

const pause = (ms: number): Promise<void> =>
    new Promise((resolve): void => {
        setTimeout(resolve, ms);
    });

export const establishConnection = (): Promise<void> => {
    LOG.info("Initiating connection with DB at %s", URI);

    return connectToDatabase(URI, opts)
        .then((result) => {
            LOG.info("Connection with DB has been established");
            connection = result;
        })
        .catch((err) => {
            LOG.error("Unable to establish connection with %s, retrying...", URI);
            LOG.error(err);
            return pause(5000).then(establishConnection); //retry after 5 seconds
        });
};

Answer 2

Upon reviewing the feedback, I successfully restructured the function to ensure it returns a promise that resolves only when the connection is established:

const pause = (ms: number): Promise<void> =>
    new Promise((resolve): void => {
        setTimeout(resolve, ms);
    });

export const establishConnection = (): Promise<void> => {
    LOG.info("Initiating connection with DB at %s", URI);

    return connectToDatabase(URI, opts)
        .then((result) => {
            LOG.info("Connection with DB has been established");
            connection = result;
        })
        .catch((err) => {
            LOG.error("Unable to establish connection with %s, retrying...", URI);
            LOG.error(err);
            return pause(5000).then(establishConnection); //retry after 5 seconds
        });
};

Timeout with Promise

Answer №1

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